1. Technical Field
The present invention relates to an interference filter, an optical filter device, an optical module, an electronic apparatus, a manufacturing method of the interference filter, and a MEMS element.
2. Related Art
In the related art, various Micro Electro Mechanical System (MEMS) elements are known, such as an interference filter in which reflective films are respectively disposed so as to face each other with a predetermined gap on surfaces of a pair of substrates facing each other, a mirror element in which a reflective film is disposed on a substrate, or a piezoelectric vibration element in which a piezoelectric body such as a quartz crystal vibrator element is disposed on a substrate.
In addition, as an example of the MEMS element, a wavelength variable interference filter is known in which electrodes are respectively provided on a pair of substrates and which includes an extraction electrode extracted from the electrode provided on one substrate, an extraction electrode provided on the other substrate, and a connection portion which brings the extraction electrodes into contact with each other for electrical connection (for example, refer to JP-A-2012-168438).
The wavelength variable interference filter disclosed in JP-A-2012-168438 is an example of the MEMS element, and the wavelength variable interference filter includes a pair of substrates (a fixed substrate and a movable substrate) on which driving electrodes are respectively provided. The fixed substrate is provided with a protrusion which protrudes toward the movable substrate, and a conduction electrode which extends from an end surface on the movable substrate side of the protrusion to an outer circumferential edge the fixed substrate. In addition, in the movable substrate, a groove is provided through etching at a position corresponding to the protrusion on a surface on an opposite side to the surface facing the fixed substrate, and a bottom of the groove is a thin portion which is flexible. Further, the extraction electrode is provided on the surface of the movable substrate facing the fixed substrate from the driving electrode to the thin portion, and the conduction electrode on the protrusion is in contact with the extraction electrode on the thin portion. In this case, the thin portion is elastically deformed, and thus contact pressure of the extraction electrode and the conduction electrode improves so that connection reliability is ensured. In addition, the thin portion is deflected so that parallelism between the pair of substrates is maintained.
However, in a case where the groove is formed through etching in the wavelength variable interference filter disclosed in JP-A-2012-168438, unless an area of the groove is sufficiently secured in a plan view in which the wavelength variable interference filter is viewed from a thickness direction, an etchant does not sufficiently flow to a deep part of the groove, and it is not easy to make the thin portion sufficiently thin.
In a case where the thin portion cannot be made sufficiently thin, deflection of the thin portion becomes insufficient, and thus the movable substrate is deflected by a pressing force of the protrusion, or the movable substrate is tilted with respect to the fixed substrate.